With the advent of biocompatible materials, the use of surgical implants in the correction of physical disorders has grown to become commonplace. These implantable devices are typically sized to be as unobtrusive as possible, while still maintaining the desired end result. Using such devices, numerous medical procedures can be accomplished that were impossible just years prior.
One type of implantable device is used in the correction of abnormal spinal curvature. Inherent in all human spines is some degree of curvature, as the spine is a highly flexible structure, capable of a high degree of movement and twist in a plurality of directions. Inherent in such flexibility, however, are instances where this curvature has becomes excessive. In such situations, the use of surgical implant devices becomes necessary.
One such example of excessive spinal curvature, namely lateral spinal deviation, is scoliosis. Scoliosis results in a sequential misalignment of the bones and intervertebral discs of the spine, and may result in pain, neurological disability or, in extreme cases, complete disability of a patient. The cause of scoliosis may be idiopathic in nature, may be due to congenital developmental disorders, or may be the result of a neuromuscular disease such as cerebral palsy.
A patient suffering from scoliosis will have a curved spine exhibiting a concave and a convex side. Scoliosis correction surgery generally requires that a plurality of hooks or screws are implanted into the spinal bones of a scoliosis patient. Attached to these hooks and screws are one or more adjustable rods, wherein the length of the rod can be varied. In correcting mild cases of scoliosis a rigid rod arrangement can be implanted along the concave side of the spine such that the rigid rod is used in maintaining the shape of the spine following a manual straightening. For example, during an invasive surgical procedure, a surgeon will manually straighten the spine and then tension the rigid rod arrangement along the concave side of the spine. Following the orientation of the rigid rod along the concave side of the spine, the newly straightened spinal column will typically retain the new shape. In cases where several manual straightenings are required, a second rigid rod may be implanted along the convex side of the spine to aid in maintaining the position of the corrected spinal column.
Existing spinal correction implants for use in correcting scoliosis typically have a mechanism wherein the length of the rods in the implants can be adjusted. Such adjustability is required because during the initial manual straightening the lengths of the rigid rods must be initially adjusted. Furthermore, when dealing with a patient requiring extensive spinal correction it is oftentimes necessary to approach total spinal straightening in stages. For example, an initial manual correction by a surgeon may be performed that roughly approximates the intended final position of the spine. After some period of time, a patient typically undergoes another surgical procedure where the spine is again manually straightened and the length of the attached rods readjusted. Existing implanted rod adjustment is currently performed using a ratcheting mechanism wherein a large incision is made such that the required ratcheting hardware can be inserted into the patient for use in adjusting the length of the rods.
Additionally, as scoliosis correction surgery is oftentimes performed on young patients, there exists a need to continually adjust the length of the surgically implanted rods as the patient grows and the length of the spinal column increases. Traditional correction techniques thereby require that the patient undergo continual invasive surgical procedures wherein the aforementioned ratcheting mechanism is used to adjust the length of the implanted surgical rods to correct for the lengthening of the spinal column of a growing patient. Such medical procedures oftentimes require large incisions to gain access to the rod adjusting mechanism and result in patient trauma and the risk of infections. In light of these facts, the time period between length adjustments of implanted surgical devices is oftentimes extended unnecessarily such that the patient does not need to undergo the pain and inconvenience of an invasive surgical procedure.